Jeroen Snelders

Conversion of (Ligno)Cellulose Feeds to Isosorbide with Heteropoly Acids and Ru on Carbon

The catalytic valorization of cellulose is currently subject of intense research. Isosorbide is among the most interesting products that can be formed from cellulose as it is a potential platform molecule and can be used for the synthesis of a wide range of pharmaceuticals, chemicals, and polymers. A promising direct route from cellulose to isosorbide is presented in this work. The strategy relies on a one-pot bifunctional catalytic concept, combining heteropoly acids, viz. H(4)SiW(12)O(40), and redox catalysts, viz. commercial Ru on carbon, under H(2) pressure. Starting from pure microcrystalline cellulose, a rapid conversion was observed, resulting in over 50% isosorbide yield. The robustness of the developed system is evidenced by the conversion of a range of impure cellulose pulps obtained by organosolv fractionation, with isosorbide yields up to 63%. Results were compared with other (ligno)cellulose feedstocks, highlighting the importance of fractionation and purification to increase reactivity and convertibility of the cellulose feedstock.

Biorefining of wheat straw using an acetic and formic acid based organosolv fractionation process

To assess the potential of acetic and formic acid organosolv fractionation of wheat straw as basis of an integral biorefinery concept, detailed knowledge on yield, composition and purity of the obtained streams is needed. Therefore, the process was performed, all fractions extensively characterized and the mass balance studied. Cellulose pulp yield was 48% of straw dry matter, while it was 21% and 27% for the lignin and hemicellulose-rich fractions. Composition analysis showed that 67% of wheat straw xylan and 96% of lignin were solubilized during the process, resulting in cellulose pulp of 63% purity, containing 93% of wheat straw cellulose. The isolated lignin fraction contained 84% of initial lignin and had a purity of 78%. A good part of wheat straw xylan (58%) ended up in the hemicellulose-rich fraction, half of it as monomeric xylose, together with proteins (44%), minerals (69%) and noticeable amounts of acids used during processing.

Ferulic Acid content and appearance determine the antioxidant capacity of arabinoxylanoligosaccharides.

To investigate the antioxidant capacity of ferulic acid (FA) in conjunction with prebiotic arabinoxylanoligosaccharides (AXOS), procedures for the production of FA-enriched, -depleted and cross-linked AXOS were developed, and samples were analyzed using the Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays. Results showed that not only the level of FA but also the condition under which it appears (free, bound, or dimerized) impacts the antioxidant capacity of FA-containing AXOS samples. Although esterification of FA on AXOS and cross-linking of AXOS through dehydrodiferulic acid formation lowered the antioxidant capacity of FA by 30 and 55%, respectively, as determined with the TEAC test, the antioxidant capacity of these components still remained high compared to Trolox, a water-soluble vitamin E analog. Total antioxidant capacity of the AXOS samples determined by the ORAC assay resulted in less prominent differences between the different forms of FA than those seen with the TEAC test. Feruloylated AXOS can hence function as strong, water-soluble antioxidants.

Impact of wheat bran derived arabinoxylanoligosaccharides and associated ferulic acid on dough and bread properties.

The impact of arabinoxylanoligosaccharides (AXOS) with varying bound or free ferulic acid (FA) content on dough and bread properties was studied in view of their prebiotic and antioxidant properties. AXOS with an FA content of 0.1-1.7% caused an increase in dough firmness with increasing AXOS concentration. AXOS with a high FA content (7.2%), on the contrary, resulted in an increase in dough extensibility and a decrease in resistance to extension, similar to that for free FA, when added in levels up to 2%. Higher levels resulted in unmanageable dough. A limited impact on dough gluten network formation was observed. These results suggest that for highly feruloylated AXOS, the FA-mediated dough softening supersedes the firming effect displayed by the carbohydrate moiety of AXOS. The impact of the different AXOS on bread volume, however, was minimal. Furthermore, AXOS in bread were not engaged in covalent cross-linking and significantly increased its antioxidant capacity.